This invention relates generally to the art of fuel utilization systems, and more particularly to the art of a fuel utilization system for use with dual-tank fuel systems.
It has been common in the past with multiple-tank fuel systems to employ crossover lines cooperating with the bottom walls of the tanks in order to allow gravity to force flow through the lines. U.S. Pat. No. 3,981,321 discloses an above-tank crossover line for multiple-tank fuel systems. U.S. Pat. No. 4,930,537 discloses a vehicle multiple-tank fuel system for a truck utilizing an above-tank crossover line coupling a primary and a secondary tank, a draw line coupled only to the primary tank and a return line coupled to the crossover line or to either of the tanks separately. The crossover line upon which this system depends is intended to function as a siphon to maintain equal levels in the primary and secondary tanks. U.S. Pat. No. 3,503,412 discloses a two tank bulk fluid system comprising manually operated rotary valves. The prior art usage of below-tank crossover lines to couple multiple-tank fuel systems makes such crossover lines subject to damage and subsequent fuel spills because of their location. The use of an above-tank crossover line in a multiple-tank fuel system has proven by past experience to be somewhat unreliable in a dynamic application such as a highway truck, because such crossover lines act as siphon tubes and are influenced by very small pressure differentials and are very susceptible to entrained gases in the fluid. The operation of a highway truck creates considerable fluid dynamics within the fuel tanks resulting in pressure differentials at the siphon tube ends sufficient to disrupt or even reverse the fluid flow. Entrained gases in the fuel will seek the highest point in a system and, therefore, accumulate in the upper part of the siphon line. Accumulation of such gases in this portion of the siphon line will cause liquid flow to cease. The use of rotary valves to switch fuel supply momentarily stops the flow of fuel until the switching process is completed. Momentary stopping of both the supply and returned fuel flow of an operating heavy duty diesel engine would result in an immediate power loss and possible damage to various components of the engine fuel system.
For the reasons discussed above, it is evident that much room for improvement exists in the art of fuel utilization systems for multiple, and more specifically, dual-tank fuel systems.